The invention concerns a draft tongue for a power-driven machine including a power transmission shaft and a coupling arrangement, that can pivot with respect to the draft tongue and is adapted for being coupled to the draft links of a towing vehicle.
Draft tongues are used to couple machines to vehicles, for example, agricultural tractors, in order to be able to pull them across a field, a street or the like. If the machine, for example, a mower, is also powered during the travel, then an articulated power take-off (PTO) shaft or the like usually extends to the vehicle in order to be able to transmit power. During travel around curves the relative position between the machine and therewith its draft tongue and PTO shaft on the one hand and the vehicle on the other hand changes. As soon as the PTO shaft exceeds an angle of a certain amount with its driven shaft due to the travel around a curve, trouble free transmission of torque is no longer possible.
In order to avoid problems in the transmission of torque during travel around a curve, it has been proposed (U.S. Pat. No. 4,525,987 granted on Jul. 2, 1985 and U.S. Pat. No. 4,738,461 granted on Apr. 19, 1988) that the implement include a pivoting drive having two drive housings that can pivot with respect to each other about a vertical axis, where the input side of the drive housing is constantly oriented towards the vehicle by a coupling arrangement; for this purpose it is connected to a pivoting hitch or to the lower draft links or arms of a three-point implement hitch.
Due to cost limitations, other machines do not use a pivoting drive, and the distance between the connecting points of the articulated PTO shaft is made as large as possible in order to keep its deviation from the extended line as low as possible. In this case the draft tongue has an articulated connection with the tractor hitch.